Microwave diode bad?

I have an older, 1998 GE Microwave oven. By the LG parts inside,
probably just a rebadged LG. Lately, it's tended to 'thunk' when the
magnetron turns on. A few times, it started rapidly cycling. Once, I
didn't stop it in time and it blew it's 20A fuse. Another time, just
starting normally, it tripped a circuit breaker.

I opened it up and checked. So far, the only obvious thing I can see is
that the large diode between the transformer and ground may be open. I
get infinite resistance in both directions. I assume there is nothing
special about testing these types of diodes?

It's an HVR-1X diode. This appears, based on some Googling, to be very
common, and the HVR-1X3 seems to be a common replacement.

Do the symptoms I describe seem to go with the way the microwave is
acting? I'm not certain just what the true function of the diode is in
this case (I know how a diode itself works). There is also what looks
like a starter cap. It's rated at 1uF, and my meter says 1.15uF or so.

Do you think it's worth trying to replace it? I did buy a replacement
microwave, but regret it. It's basically the same, but has some issues I
don't like (display too far back from front, so you have to squat down
to see it while typing on the panel. Fan goes REAL fast when magnetron
off, then seems to nearly die when it's on.)

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In article <>, says...
> >It's an HVR-1X diode. This appears, based on some Googling, to be
very
> >common, and the HVR-1X3 seems to be a common replacement.
>
> That diode is spec'ed at having a large forward voltage drop (10-14
> volts). I regular ohm meter will not provide a voltage that high and
> will show open.

Is there a simple setup I can create to test it?

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In article <-september.org>,andysnewsreply@no_junk.comcast.net says...
>
> In article <>,
> says...
> > >It's an HVR-1X diode. This appears, based on some Googling, to be
> very
> > >common, and the HVR-1X3 seems to be a common replacement.
> >
> > That diode is spec'ed at having a large forward voltage drop (10-14
> > volts). I regular ohm meter will not provide a voltage that high and
> > will show open.
>
> Is there a simple setup I can create to test it?

I guess I'll answer my own question! I used a 12V UPS battery I had
(12.89V measured) and checked if I could measure voltage through it. The
diode does work and measured about 9.5V.

Any other ideas on what could cause the power surge when the magnetron
is activated? The waveguide is clean. I removed the mica cover over it,
and there was nothing inside.

--
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Andrew Rossmann wrote:
> I have an older, 1998 GE Microwave oven. By the LG parts inside,
> probably just a rebadged LG. Lately, it's tended to 'thunk' when the
> magnetron turns on. A few times, it started rapidly cycling. Once, I
> didn't stop it in time and it blew it's 20A fuse. Another time, just
> starting normally, it tripped a circuit breaker.
>
> I opened it up and checked. So far, the only obvious thing I can see is
> that the large diode between the transformer and ground may be open. I
> get infinite resistance in both directions. I assume there is nothing
> special about testing these types of diodes?
>
> It's an HVR-1X diode. This appears, based on some Googling, to be very
> common, and the HVR-1X3 seems to be a common replacement.
>
> Do the symptoms I describe seem to go with the way the microwave is
> acting? I'm not certain just what the true function of the diode is in
> this case (I know how a diode itself works). There is also what looks
> like a starter cap. It's rated at 1uF, and my meter says 1.15uF or so.
>
> Do you think it's worth trying to replace it? I did buy a replacement
> microwave, but regret it. It's basically the same, but has some issues I
> don't like (display too far back from front, so you have to squat down
> to see it while typing on the panel. Fan goes REAL fast when magnetron
> off, then seems to nearly die when it's on.)
>
That diode you speak of can not be tested in a conventional DIODE test
in a DMM. It has several single diodes in series to up the over all
operating voltage, each one ~ 0.6 volt drop. Most basic diode modes in
DMM will only cover up to 2/3 in series. Long story short, you need
more voltage to be applied to the diode for a test. Some of us have
HV variable supplies, some crude, some elegant, like mine

A Varistate, HV transformer and HV probe works well to test these.

Jugging from your description, my guess would be a bad magnetron, one
that has an intermitting short.

Andrew Rossmann wrote:
> In article <-september.org>,
> andysnewsreply@no_junk.comcast.net says...
>
>>In article <>,
>> says...
>>
>>>>It's an HVR-1X diode. This appears, based on some Googling, to be
>>
>>very
>>
>>>>common, and the HVR-1X3 seems to be a common replacement.
>>>
>>>That diode is spec'ed at having a large forward voltage drop (10-14
>>>volts). I regular ohm meter will not provide a voltage that high and
>>>will show open.
>>
>>Is there a simple setup I can create to test it?
>
>
> I guess I'll answer my own question! I used a 12V UPS battery I had
> (12.89V measured) and checked if I could measure voltage through it. The
> diode does work and measured about 9.5V.
>
> Any other ideas on what could cause the power surge when the magnetron
> is activated? The waveguide is clean. I removed the mica cover over it,
> and there was nothing inside.
>
Doing a forward test on a HV diode does not mean it's good, you still
could have a break down problem with HV entered.